The present invention relates to a tool changer for use in automatic machine tools such as an NC machinery, and more particularly to a tool changer for exchanging a used tool on a spindle with a fresh one stored within the body of the spindle.
It is known in the art to employ an automatic tool changer for an NC machinery so as to avoid disrupting the operation when a used tool on the main spindle is exchanged with a fresh tool stored in the magazine. The known automatic tool changer has a fairly complicated mechanism, which includes a tool carrying arm for shifting the fresh tool from the magazine to an changer head, which then carries and mounts the fresh tool on the main spindle.
The tool carrying arm requires a relatively large working space for itself and related part members thereby increasing the sizes and prices of the tool changers.
In addition, locating the tool carrying arm exactly at a position where the tools are exchanged may be difficult and the work involved in tool locating is time-consuming. In trying to finish the tool location in a short period of time, the precision is often sacrificed. In tapping, for example, a hole is preformed by a drill, wherein the used tool is the drill, and a fresh tool is a tap. The positions of the drill and the tap are the same with respect to the workpiece. However, in order to avoid colliding with the workpiece the drill is shifted to a position where the drill is exchanged with the tap. After the drill is exchanged with the tap, the tap is shifted to a working position. In this way the known tool changers require the travel of the tool carrying arm, which consumes time. The mechanical movements generate frictional heat in the feed screws, and wear the part members engaged in the tool exchange. The tool exchange is a highly sophisticated work. Even minor inadequacy leads to imprecise location of the fresh tool. If the tool exchange takes a long time, it is particularly disadvantageous when a routine work is done with a small tool. The tool exchange should be finished as soon as possible.
The present invention is directed toward an improved tool changer which solves the problems encountered by the known tool changers discussed above. Thus, an object of the present invention is to provide an automatic tool changer capable of exchanging one tool with another in a short period of time.
Another object of the present invention is to provide an automatic tool changer capable of locating a replacing tool at an exact position with respect to the workpiece.